首页 | 官方网站   微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   37536篇
  免费   2335篇
  国内免费   210篇
医药卫生   40081篇
  2023年   372篇
  2022年   590篇
  2021年   1685篇
  2020年   1006篇
  2019年   1294篇
  2018年   1605篇
  2017年   1155篇
  2016年   1268篇
  2015年   1360篇
  2014年   1727篇
  2013年   2106篇
  2012年   3190篇
  2011年   3093篇
  2010年   1741篇
  2009年   1499篇
  2008年   2275篇
  2007年   2347篇
  2006年   2070篇
  2005年   1844篇
  2004年   1673篇
  2003年   1400篇
  2002年   1214篇
  2001年   397篇
  2000年   335篇
  1999年   302篇
  1998年   207篇
  1997年   138篇
  1996年   148篇
  1995年   111篇
  1994年   100篇
  1993年   82篇
  1992年   155篇
  1991年   165篇
  1990年   134篇
  1989年   125篇
  1988年   110篇
  1987年   104篇
  1986年   92篇
  1985年   124篇
  1984年   82篇
  1983年   54篇
  1982年   57篇
  1981年   57篇
  1980年   45篇
  1979年   55篇
  1978年   46篇
  1977年   35篇
  1975年   37篇
  1974年   39篇
  1973年   36篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Two different fabrication methods were performed and compared for preparation of binary metallic oxide microstructures supported on a reduced graphene oxide (rGO) modified graphite electrode. Nickel–Cobalt oxide microspheres (NiCo2O4 MSs) were prepared by two different deposition methods: wet chemical and in situ-electrical deposited methods. Different characterization methods were conducted, including cyclic voltammetry (CV), scanning emission microscopy (SEM), electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. The deposition methods of NiCo2O4 MSs were found to affect the electrochemical behavior of the modified electrodes towards the oxidation of venlafaxine (VEN), an anti-depressant drug. The fabricated electrode showed linearity over the range 5–500 nmol L−1 and an excellent sensitivity with a limit of detection (LOD) and limit of quantitation (LOQ) of 3.4 and 10.3 nmol L−1, respectively. It was revealed that the wet-NiCo2O4@rGO modified electrode prepared by the wet chemical method showed an improved electrochemical behavior for determination of VEN in pharmaceuticals and human plasma with high recovery results in the range of 96.7–98.6% and 96.0–100.7%, respectively without any interference from the co-existing components.

Different electrodeposited NiCo2O4 microspheres supported on a reduced graphene oxide platform for electrochemical sensing of venlafaxine.  相似文献   
992.
The modeling of long bone surfaces during linear growth is a key developmental process, but its regulation is poorly understood. We report here that parathyroid hormone‐related peptide (PTHrP) expressed in the fibrous layer of the periosteum (PO) drives the osteoclastic (OC) resorption that models the metaphyseal–diaphyseal junction (MDJ) in the proximal tibia and fibula during linear growth. PTHrP was conditionally deleted (cKO) in the PO via Scleraxis gene targeting (Scx‐Cre). In the lateral tibia, cKO of PTHrP led to a failure of modeling, such that the normal concave MDJ was replaced by a mound‐like deformity. This was accompanied by a failure to induce receptor activator of NF‐kB ligand (RANKL) and a 75% reduction in OC number (P ≤ 0.001) on the cortical surface. The MDJ also displayed a curious threefold increase in endocortical osteoblast mineral apposition rate (P ≤ 0.001) and a thickened cortex, suggesting some form of coupling of endocortical bone formation to events on the PO surface. Because it fuses distally, the fibula is modeled only proximally and does so at an extraordinary rate, with an anteromedial cortex in CD‐1 mice that was so moth‐eaten that a clear PO surface could not be identified. The cKO fibula displayed a remarkable phenotype, with a misshapen club‐like metaphysis and an enlargement in the 3D size of the entire bone, manifest as a 40–45% increase in the PO circumference at the MDJ (P ≤ 0.001) as well as the mid‐diaphysis (P ≤ 0.001). These tibial and fibular phenotypes were reproduced in a Scx‐Cre‐driven RANKL cKO mouse. We conclude that PTHrP in the fibrous PO mediates the modeling of the MDJ of long bones during linear growth, and that in a highly susceptible system such as the fibula this surface modeling defines the size and shape of the entire bone.  相似文献   
993.
Colon cancer is a complex disease that involves numerous genetic alterations that change the normal colonic mucosa into invasive adenocarcinoma. In the current study, the protective effects of inulin (prebiotic), Lactobacillus casei (L. casei, probiotic) and their combination (synbiotic) on 1,2-dimethylhydrazine (DMH)-induced colon cancer in male Swiss mice were evaluated. Animals were divided into: Control group, DMH-treated group, DMH plus inulin, DMH plus L. casei and DMH plus inulin plus L. casei-treated groups. Fecal microbiome analysis, biochemical measurements, histopathological examination of the colon tissues, immunostaining and Western blotting analysis of β-catenin, GSK3β and JNK-1 were performed. The prebiotic-, probiotic- and synbiotic-treated groups showed decreased levels of carcinoembryonic antigen and a lower number of aberrant crypt foci compared to the DMH-treated group with the synbiotic group exhibiting a superior effect. Furthermore, all treatments showed a body weight-reducing effect. Administration of inulin, L. casei or their combination increased the expression level of phospho-JNK-1 while they decreased the expression level of β-catenin and phospho-GSK3β. Remarkably, L. casei treatment resulted in enrichment of certain beneficial bacterial genera i.e. Akkermansia and Turicibacter. Therefore, administration of L. casei and inulin as a synbiotic combination protects against colon cancer in mice.

The lactobacillus casei and inulin modulate the expression of JNK-1, GSK3β and β-catenin proteins and enrich the beneficial bacteria to protect from colon cancer in mice.  相似文献   
994.
995.

Objective

To estimate the frequency of acquired ADAMTS13 deficiency in severe cases of Hemiscorpius lepturus stung patients and the frequency of acute kidney injury (AKI) in these patients.

Methods

Sixty scorpion stung children who were referred with severe hemolysis and hemoglobinuria were studied. None of them had received blood products and no one had a past medical history of renal failure.

Results

Plasma levels of ADAMTS13 and ADAMTS13 antibody (IgG) were measured using ELISA. ADAMTS13 was decreased in 91.7 % of patients and the anti-ADAMTS13 antibody (Ab) was increased in 98.3 %. ADAMTS13 decreased in all of the patients with acute kidney injury and none of those with normal levels of ADAMTS13 developed renal failure; all patients with AKI had also increased levels of ADAMTS13Ab. Acute kidney injury was found in 23.3 % and had significant association with severe anemia, thrombocytopenia, pyuria, hematuria and considerable proteinuria (p?<?0.001). Disseminated intravascular coagulation (DIC) and Hemolytic uremic syndrome (HUS) developed in 6.7 % and 10 % respectively.

Conclusions

The index findings demonstrate that Hemiscorpius lepturus sting is usually associated with ADAMTS13 deficiency, and increased ADAMTS13 autoantibody. These combined mechanisms may contribute to scorpion sting-induced coagulopathies and may predispose patients to develop DIC and HUS.  相似文献   
996.
997.
Covalent functionalization (CF-GNPs) and non-covalent functionalization (NCF-GNPs) approaches were applied to prepare graphene nanoplatelets (GNPs). The impact of using four surfactants (SDS, CTAB, Tween-80, and Triton X-100) was studied with four test times (15, 30, 60, and 90 min) and four weight concentrations. The stable thermal conductivity and viscosity were measured as a function of temperature. Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) and Raman spectroscopy verified the fundamental efficient and stable CF. Several techniques, such as dispersion of particle size, FESEM, FETEM, EDX, zeta potential, and UV-vis spectrophotometry, were employed to characterize both the dispersion stability and morphology of functionalized materials. At ultrasonic test time, the highest stability of nanofluids was achieved at 60 min. As a result, the thermal conductivity displayed by CF-GNPs was higher than NCF-GNPs and distilled water. In conclusion, the improvement in thermal conductivity and stability displayed by CF-GNPs was higher than those of NCF-GNPs, while the lowest viscosity was 8% higher than distilled water, and the best thermal conductivity improvement was recorded at 29.2%.

Covalent functionalization (CF-GNPs) and non-covalent functionalization (NCF-GNPs) approaches were applied to prepare graphene nanoplatelets (GNPs).  相似文献   
998.
999.
Hyperuricemia (HUA), a disease due to an elevation of body uric acid level and responsible for various diseases such as gout, cardiovascular disorders, and renal failure, is a major ground debate for the medical science these days. Considering the risk factors linked with allopathic drugs for the treatment of this disease, the debate has now become a special issue. Previously, we critically discussed the role of dietary polyphenols in the treatment of HUA. Besides dietary food plants, many researchers figure out the tremendous effects of medicinal plants‐derived phytochemicals against HUA. Keeping in mind all these aspects, we reviewed all possible managerial studies related to HUA through medicinal plants (isolated compounds). In the current review article, we comprehensively discussed various bioactive compounds, chemical structures, and structure–activity relationship with responsible key enzyme xanthine oxidase.  相似文献   
1000.
In continuation with our research program on the development of novel bioactive molecules, we report herein the design and synthesis of a series of diversified heterocycles ( 4 – 22 ). The synthesized compounds were evaluated for their anti‐inflammatory activity. The chemical structures of the newly synthesized compounds have been confirmed by NMR, FTIR, and microanalysis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号